The present invention is generally related to porous silicon substrates and, more particularly, is related to porous silicon sensors and methods of preparation thereof.
High surface area porous silicon (PS) substrates formed in wafer scale through electrochemical (EC) etching fall into two groups. PS substrates fabricated from aqueous electrolytes consist of highly branched nonporous substrates while PS substrates fabricated from a aqueous electrolyte are comprised of open and accessible macroporous substrates with deep, wide, well-ordered channels.
High-surface area silicon substrates formed in wafer scale through etching display a visible photoluminescence (PL) upon excitation with a variety of visible and ultraviolet light sources. This room-temperature luminescence has attracted considerable attention primarily because of its potential use in the development of silicon-based optoelectronics, displays, and sensors.
Although the PL is thought to emanate from regions near the PS substrate surface, the origin of the PL is the source of some controversy as the efficiency and wavelength range of the emitted light can be affected by the physical and electronic properties of the surface, the nature of the etching solution, and the nature of the environment into which the etched sample is placed. Given this range of parameters, it is surprising that, with few exceptions, PL spectra are reported for PS substrates formed in dilute aqueous HF solutions, that have already been dried in air or more inert environments following etch and rinse treatments. These ex situ samples, while providing spectral information, do not indicate the evolution of the PS substrates, and thus, they do not indicate means by which it might be modified and enhanced during or following the etch treatment.
An existing problem in fabricating PS devices rests with establishing electrical contact to the PS substrates. Another problem with PS includes the relatively long excited-state lifetime associated with the PS substrate PL. A further problem includes the relatively low PL quantum yield and the instability of the PL from PS substrates. An additional problem includes that small, sensitive, and selective sensors are not readily available at cost effective prices.
Thus, a heretofore unaddressed need exists in the industry to address the aforementioned deficiencies and inadequacies.
An embodiment of the present invention provides for a sensor. A representative sensor includes a silicon substrate having a porous silicon region. A portion of the porous silicon region has a front contact disposed thereon. The contact resistance between the porous silicon region and the front contact is between about 10 ohms and 100 ohms.
Another embodiment provides for a method of fabricating a sensor. The fabrication includes: providing a silicon substrate; converting a first region of the silicon substrate into a porous silicon region; forming a first front contact onto a first portion of the porous silicon region; and forming a second front contact onto a second portion of the porous silicon region, wherein a third portion of the porous silicon region is between the first front contact and the second front contact.
Other systems, methods, features, and advantages of the present invention will be or become apparent to one with skill in the art upon examination of the following detailed description. It is intended that all such additional systems, methods, features, and advantages be included within this description, be within the scope of the present invention, and be protected by the accompanying claims.